Car runs sick after changes

[berky2500]

Since the last time I drove the car, I have added Flowmaster 50 Series mufflers. I took it out today and it ran terrible from idle up to about 2700 rpm. It was very choppy and rough, and would also hesitate a lot. It had a really bad rumble at about 1800 rpm.

Once I put my foot into it, it would seem to run better until I left off of it then it would pop and backfire as it slowed down. It did this for about 5 miles, I was almost back home and it just seemed to start running better.

Just before the last time I drove it I replaced the oxygen sensor and fuel filter, it ran fine that day when I drove it.

Does adding the new mufflers mess with the ECM and it has to adjust things to run right again or something crazy like that? Any other ideas? I may try again tomorrow and see how it runs.

 

[Edmond]

No, changing mufflers will not change the ECM or anything like that. I can't see how the different mufflers would effect your ride quality.

I changed to Flowmasters last summer and didn't have any problems.

Have you checked to make sure the air filter and all related parts are good to go? I'm asking because I had this MAF that I cut the screens out of and that made it feel choppy.

 

[berky2500]

Ok, just had to check. I took it out today and it ran fine so I have no idea what was going on. Guess I'll just keep driving it and see what happens.

 

[ErnieN85]

Sounds to me like it got some water in the ignition wires or cap, maybe a crack or split in a boot. when it gets hot enough it'll dry up and run fine. leave it set and it drays moisture. look carefully for torn boots on the plugs. I had a hairline crack in the porcelin on a plug once after awhile (serval thousand miles) it formed a carbon trail and was visable upon inspection.

 

[berky2500]

I've just recently changed (before the mufflers and before the last time I drove it) the plugs, wires, cap, rotor and coil. I've also changed the fuel filter and oxygen sensor. The only thing I haven't changed is the air filter. The car hasn't been wet (even washed) since I put it in the garage in September.

The other thing I've noticed is that the voltage is pretty low after sitting for a while and doesn't get up above 14 volts until it is running above 2500 rpm. I usually see a direct correlation between the hesitation and low voltage, makes sense low spark or not enough. I'm thinking I have a regulator problem, but I haven't had the charging system tested yet. It is next on the list.

I also haven't put any gas in it since September, and have added no fuel stabilizer. I'm wondering if it may have drawn moisture over the winter?

If it acts up again with good voltage, I'll go back over the connections and plugs.

Thanks for the suggestions.

 

[Edmond]

The other thing I've noticed is that the voltage is pretty low after sitting for a while and doesn't get up above 14 volts until it is running above 2500 rpm. I usually see a direct correlation between the hesitation and low voltage, makes sense low spark or not enough. I'm thinking I have a regulator problem, but I haven't had the charging system tested yet. It is next on the list.

If it is the alternator, another way besides a notice in hesitation is that your mileage will have gone down. Trust me, I know from experience!:L

 

[berky2500]

The new speed sensor still hasn't come in yet so I have no speed indication, or when I do it is way off. The dash cluster has already checked out ok.

So right now my gas mileage is undetermined, hopefully soon though.

 

[oldace84]

Have you checked your converter?????
Just a thought.
tony

 

[berky2500]

The torque convertor?? Related to the lack of speedometer signal or the rough idle??

 

[Da Hawaiian Punch]

I do believe that the reason your car seemed to be running better when you got home was because of the computer finaly starting to learn the changes that you did, (Removing the muffler's)
Remember, the computer does learn to a curtain point of the chances that's been done to the car, even the trans has a learning capability.
My car did the same thing when I removed the muffler's and gutted the cat's, it ran very sluggish, and I was worried that something was seriously wrong with my car!! but it cleared up a little before I reached home, like in your case.
I'm not a master machanic or anything, so if your still unsure about theses events that were happening to you, you might ask C4C5 specialist for more clear answer's to your question's, also "Vette Chick" (I think thats the name she goes by) also has a lot of smart's when it comes to these automobiles.
Aloha my friend.
"I am Da Hawaiian Punch"

 

[berky2500]

It turns out I guess it was a combination of two things. The mufflers I think were the cause of the temporary running problems as it learned all the new parts. At least that is as plausible as anything else.

The other problem was definitely the alternator, it would not hold a good voltage output at idle, after rebuilding the alternator, I have not had any more hesitation problems.

She is actually running pretty good right now, enough so that I'm going to brave driving it to Nashville for the 50th Corvette celebration as part of the NCM Caravans. We'll see how it goes, thanks for all the replies.